The present disclosure relates generally to medical methods, systems, and devices for performing endovascular interventions. More particularly, the present disclosure relates to methods and systems for access directly into the carotid artery to perform interventional procedures in the treatment of vascular disease and other diseases associated with the vasculature.
Interventional procedures are performed to treat vascular disease, for example stenosis, occlusions, aneurysms, or fistulae. Interventional procedures are also used to perform procedures on organs or tissue targets that are accessible via blood vessels, for example denervation or ablation of tissue to intervene in nerve conduction, embolization of vessels to restrict blood flow to tumors or other tissue, and delivery of drugs, contrast, or other agents to intra or extravascular targets for therapeutic or diagnostic purposes. Interventional procedures are typically divided into coronary, neurovascular, and peripheral vascular categories. Most procedures are performed in the arterial system via an arterial access site.
Methods for gaining arterial access to perform these procedures are well-established, and fall into two broad categories: percutaneous access and surgical cut-down. The majority of interventional procedures utilize a percutaneous access. For this access method, a needle puncture is made from the skin, through the subcutaneous tissue and muscle layers to the vessel wall, and into the vessel itself. Vascular ultrasound is often used to image the vessel and surrounding structures, and facilitate accurate insertion of the needle into the vessel. Depending on the size of the artery and of the access device, the method will vary, for example a Seldinger technique or modified Seldinger technique consists of placing a sheath guide wire through the needle into the vessel. Typically the sheath guide wire is 0.035″ or 0.038″. In some instances, a micro-puncture or micro access technique is used whereby the vessel is initially accessed by a small gauge needle, and successively dilated up by a 4 F micropuncture cannula through which the sheath guidewire is placed. Once the guidewire is placed, an access sheath and sheath dilator are inserted over the guide wire into the artery. In other instances, for example if a radial artery is being used as an access site, a smaller sheath guidewire is used through the initial needle puncture, for example an 0.018″ guidewire. The dilator of a radial access sheath is designed to accommodate this smaller size guidewire, so that the access sheath and dilator can be inserted over the 0.018″ wire into the artery.
In a surgical cut-down, a skin incision is made and tissue is dissected away to the level of the target artery. This method is often used if the procedure requires a large access device, if there is risk to the vessel with a percutaneous access, and/or if there is possibility of unreliable closure at the access site at the conclusion of the procedure. Depending on the size of the artery and of the access device, an incision is made into the wall of the vessel with a blade, or the vessel wall is punctured directly by an access needle, through which a sheath guide wire is placed. The micropuncture technique may also be used to place a sheath guide wire. As above, the access sheath and sheath dilator are inserted into the artery over the sheath guide wire. Once the access sheath is placed, the dilator and sheath guide wire are removed. Devices can now be introduced via the access sheath into the artery and advanced using standard interventional techniques and fluoroscopy to the target site to perform the procedure.
Access to the target site is accomplished from an arterial access site that is easily entered from the skin. Usually this is the femoral artery which is both relatively large and relatively superficial, and easy to close on completion of the procedure using either direct compression or one of a variety of vessel closure devices. For this reason, endovascular devices are specifically designed for this femoral access site. However, the femoral artery and its vicinity are sometimes diseased, making it difficult or impossible to safely access or introduce a device into the vasculature from this site. In addition, the treatment target site may be quite some distance from the femoral access point requiring devices to be quite lengthy and cumbersome. Further, reaching the target site form the femoral access point may involve traversing tortuous and/or diseased arteries, which adds time and risk to the procedure. For these reasons, alternate access sites are sometimes employed. These include the radial, brachial and axillary arteries. However, these access sites are not always ideal, as they involve smaller arteries and may also include tortuous segments and some distance between the access and target sites.
Some Exemplary Issues with Current Technology
In some instances, a desired access site is the carotid artery. For example, procedures to treat disease at the carotid artery bifurcation and internal carotid artery are quite close to this access site. Procedures in the intracranial and cerebral arteries are likewise much closure to this access site than the femoral artery. This artery is also larger than some of the alternate access arteries noted above. (The common carotid artery is typically 6 to 10 mm in diameter, the radial artery is 2 to 3 mm in diameter.)
Because most access devices used in interventional procedure are designed for the femoral access, these devices are not ideal for the alternate carotid access sites, both in length and mechanical properties. This makes the procedure more cumbersome and in some cases more risky if using devices designed for femoral access in a carotid access procedure. For example, in some procedures it is desirable to keep the distal tip of the access sheath below or away from the carotid bifurcation, for example in procedures involving placing a stent at the carotid bifurcation. For patients with a low bifurcation, a short neck, or a very deep carotid artery, the angle of entry of the sheath into the artery (relative to the longitudinal axis of the artery) is very acute with respect to the longitudinal axis of the artery, i.e. more perpendicular than parallel relative to the longitudinal axis of the artery. This acute angle increases the difficulty and risk in sheath insertion and in insertion of devices through the sheath. In these procedures, there is also risk of the sheath dislodgement as only a minimal length of sheath can be inserted. In femoral or radial access cases, the sheaths are typically inserted into the artery all the way to the hub of the sheath, making sheath position very secure and parallel to the artery, so that the issues with steep insertion angle and sheath dislodgement do not occur in femoral access sites.
In other procedures, it is desirable to position the sheath tip up to and possibly including the petrous portion of the internal carotid artery, for example in procedures requiring access to cerebral vessels. Conventional interventional sheaths and sheath dilators are not flexible enough to be safely positioned at this site.
In addition, radiation exposure may be a problem for the hands of the operators for procedures utilizing a transcarotid access site, if the working areas are close to the access site.